Analytical Chemistry
1991
City University of New York
1991
See all Profiles
Faculty
Faculty
Charles Hosten
Faculty Coordinator, Academic Mentoring Program
Department/Office
- Center for Academic Excellence
School/College
- College of Arts & Sciences
Education & Expertise
Education
Analytical Chemistry
B.Sc.
University of the West Indies
. 1982
Research
Research
Specialty
Vibrational Spectroscopy and ElectrochemistryFunding
National Science FoundationNational Cancer InstituteDepartment of Defense
Related Articles
Probing the adsorption and orientation of 2,3-dichloro-5,8-dimethoxy-1,4-naphthoquinone on gold nano-rods: A SERS and XPS study.
Journal of Molecular StructureAuthors: Maraizu Ukaegbu, Nkechi Enwerem, Oladapo Bakare, Vichetra Sam, William Southerland, Alberto Vivoni, Charles Hostenhttps://doi.org/10.1016/j.molstruc.2016.02.0432, 3-Dichloro-5,8-dimethoxy-1,4-naphthoquinone (DDNQ) is a synthetic naphthaquinone which has shown reduced chemotoxicity and enhanced chemotherapeutic activity in in vitrostudies. The ability of DDNQ to serve as a chemical dopant of graphene resulting improved performance of graphene by tuning its band gap is also being explored. In this report surface enhanced Raman scattering (SERS) spectroscopy was utilized to probe the adsorption/orientation of DDNQ on gold nano-rods. Interpretation of the SERS data required a complete assignment of the vibrational modes of DDNQ and this was performed with DFT calculations using BP86/6-31G (d, p), B3LYP/6-31G (d) basis sets, and potential energy distribution (PED) calculations. Surface selection rules and relative band enhancement factors were utilized to propose an orientation and mode of interaction for DDNQ adsorbed on Au nanosurfaces. XPS data supported the conclusions obtained from the SERS data.
Determination of molecular orientation and order of N-(6-Mercaptoacetylhexyl)quinolinium tricyanoquinodimethanide adsorbed on Ag nanoparticles
Journal of Colloid and Interface ScienceAuthors: Melissa C. Fletcher, Dimitri Alexson, Sharka M. Prokes, Orest J. Glembocki, Alberto Vivon, Charles M. Hostenhttps://doi.org/10.1016/j.jcis.2015.02.052The surface-enhanced and tip-enhanced Raman scattering spectra of N-(6-Mercaptoacetylhexyl) quinolinium tricyanoquinodimethanides on silver coated nanosurfaces have been obtained, analyzed using Density Functional Theory Calculations, and a complete list of frequencies and assignments for the molecules are presented. The spectroscopic evidence points to the fact that monolayers of the molecule can be formed through the self-assembly process and the SERS data indicate that the monolayer attach to the silver surface through the nitrile groups. SERS spectroscopy was useful in determining the orientation of the monolayer as well as estimating its order. Deprotection the thiol group thereby terminating the tail of the molecule with a sulfur atom allowed for a selectively oriented monolayer to be formed which permanently bound the molecules to the surface preventing rearrangements. This orientation of AcSC6H12Q-3CNQ on silver a surface allowed the electron pairs of the nitrogen to be available for interaction with a second contact. Based on trigonometric tangent function calculations the tilt angle was calculated to be 38 for the protected molecule and 70 for the deprotected alkane thiol monolayer.
Tip enhanced Raman spectroscopy, DFT and PED calculations of 4″-trimethylsilylethylsulfanyl-4,4′-di(phenyleneethynylene)benzene thiol adsorbed on silver
Journal of Molecular Structurehttps://doi.org/10.1016/j.molstruc.2015.07.006Monolayers of a,u-dithiol oligo(phenyleneethynlene) molecules are critical to the field of molecular electronics because of their abilities to form bonds with many metallic surfaces and rectify current. In this study Fourier Transformation-Raman, surface-enhanced Raman scattering (SERS) spectroscopy and Tip-enhanced Raman Spectroscopy (TERS) were used to characterize a selectively oriented selfassembled monolayer of 400-trimethylsilylethylsulfanyl-4,40 -bis-(phenyleneethynylene)benzenethiol (OPE0 ) on silver coated nanospheres. Selective orientation was achieved by synthesizing 400-trimethylsilylethylsulfanyl-4,40 -bis-(phenyleneethynylene)benzene disulfide, which undergoes oxidative dissociation and covalently bonds to the metal surface. The Ag coated nanosphere surfaces were characterized by scanning electron microscopy (SEM), which showed a large area of surface charging. The SERS and TERS spectra show similar results; however, a greater enhancement was achieved with the TERS relative to the SERS spectra. Assignments of vibrational bands were based on DFT calculations performed at the B3LYP level with good agreement between theoretical and experimental values. An average percent difference of 2.5 cm1 was obtained for the non-CH stretching frequencies and a scaling factor was not applied to theoretically generated frequencies. A red shift of the n(CeS) peak at 1087 cm1 was observed when OPE0 was adsorbed on a Ag surface. Vibrations specific to the trimethylsilylethyl (TMSE) group were visible in the TERS spectra, and disappear upon deprotection